1.1 INTRODUCTION TO AS/400
AS/400 is a 100% IBM Mid-range server.
Introduced way back in 1985 it is well accepted in industry all over the world.
Today it enjoys the reputation of being considered as the one of the most
stable Database Servers in the world. It has some outstanding features that
practically no other server might be having.
These
features are:
1.
Not
a single virus was ever discovered on an AS/400 system.
2.
Practically
every bank world over uses AS/400 to store its customer database.
3.
Large
number of Mechanical Engineering and other companies use AS/400 since it Supports
the most popular ERP software such as JD Edwards, MAPICS and BPCS
4.
It
is a truly 24/7/365 system. Very few re-boots may be required throughout the year.
Certain functional sections of the Operating system (called Subsystems may be shut
down temporarily for routine maintenance). In most cases rebooting is not required.
5.
Not
a single Hacking attempt has been recorded for an AS/400 system. Practically every
server in the world has been hacked successfully till date.
6.
AS/400
contains all software internally designed and developed by IBM. This as resulted
in a very stable and robust system with programming as well as Database serving
capabilities.
Its
main application is of a Database Server although many other diverse
applications are well supported and implemented lately.
Sign On:
The First
AS/400 screen is normally the sign on screen where you must provide a proper username
and password. The AS/400 screen is green in colour having background as black,
that's why we call it as green screen:
1.2 BASIC TERMS
ü
Library
A Library is a container: a logical
partition in which Objects can be placed and secured. AS/400 follows a flat
file system; no two libraries can have the same name as they are all at the
same level. There is no provision of library inside a library (exception; QSYS library
contains all the libraries). Library name cannot exceed 10 characters, cannot contain
embedded spaces and it is preferred that you should not start your library with
letter Q (because all the system libraries name start with letter Q). Basically
Libraries are classified as *TEST (test) and *PROD (product) depending on
whether the Library contain tested and deployed software (Product) which is
being used for Production purpose.
ü
Library list
When you call a program, (using CALL
CL command) where does AS/400 search for this program? It searches a list called library list.
Suppose we type CALL RP001 in order to run this program. Libraries L1, L2 and
L3 are currently present in the Library list. AS/400 first looks for this
program in L1, if it is found it is executed otherwise it will search in Library
L2, then L3. If none of these libraries have RPO01, and error message is given
(File not found in *LIBL). Thus one of the first things that you do when you
login (Sign on) is to update your library list. Contents of the Library list
are lost when you sign off. Library list can be edited using EDTLIBL Command
(OR directly by using ADDLIBLE). We shall implement Library list in the second
chapter.
ü
Object
An AS/400 Object occupies space on the
magnetic storage and serves 'some useful purpose. Mostly, everything or AS/400
is an object. There are pre-defined object types, which we can create on this
server, Objects have properties called Attributes.
ü Object
Types
Object types start with an asterisk.
For example executable program has a *PGM object type. A Database file has a
*FILE object type. There are more than 80 types of objects in AS/400.
ü ASP
(Auxiliary Storage Pool)
AS/400 manages magnetic storage in the
form of Auxiliary Storage Pool (ASP). IT consists of several hard drives whose
magnetic space is used as a whole.
ü Member
Member can be approximately compared with
a file in MS DOS. Source code, or plain text (like a Readme file) can be placed
in a member. Member cannot directly exist in a library since it is not an
AS/400 object. It is associated with a Source Physical File as explain in the
following paragraph. Member contains program source code; such as CL and RPG
programs or even COBOL and Pascal program. Depending on the language, the type of
the member is specified; For example, for a member containing a CL program, the
type is specified as CLP and for a member containing RPG program, the type is
RPG.
ü Source
Physical file
This is a dedicated object that houses
one or more members. Multiple members can be grouped under a source physical
file. A project may consist of many source Physical files. Source Physical file
is a valid AS/400 object and hence can exist inside a library.
ü WRKMBRPDM
It is a utility to Work with Members
(WRKMBRPDM: Work With members using Program Development Manager). Type
WRKMBRPDM to start working in the start working in the Programming Development
Manager.
Using this utility, we can add /
rename/ change/ or start editing a member. It can also be used to compile a
program member: such as RPG program, CL program, COBOL program etc.
WRKMBRPDM Consists of 2 menu sets:
Numeric and Function key menu. To change or edit existing members, use the
numeric options. Function options can be used to perform other tasks; like
creating a member.
When you start WRKMBRPDM, it asks for
the name. of Source Physical file to open and its location (Library), after
inputting the necessary data, WRKMBRPDM displays the members in the source
physical file in a tabular fashion.
Modules of AS/400:-
There four modules of it:- DB2/400 (Database)
- CL/400 (Control Language)
- RPG (Report Program Generator )
- ILE (Integrated Language Environment)
